NEW YORK – A large, at-home antibody testing program in the UK has yielded its first results, the UK Department of Health and Social care reported on Thursday.
Between June 20 and July 13, 100,000 volunteers tested themselves at home using finger prick tests to check if they had developed antibodies against SARS-CoV-2, the virus that causes COVID-19. Study participants tested themselves using a lateral flow immunoassay manufactured by Fortress Diagnostics, an in vitro diagnostics manufacturer based in Antrim, Northern Ireland.
The testing was carried out as part of the government-funded National Real-time Assessment of Community Transmission-2 (REACT-2) seroprevalence study and led by investigators at Imperial College London. The first findings were made available freely as a preprint on Aug. 12.
According to the investigators, about 3.4 million people, or 6 percent of the population in England, was likely infected by SARS-CoV-2 by July 13. However, the rates of infections varied based on different parameters. Thirteen percent of Londoners, for instance, had developed antibodies to the virus, while in the southwest of England less than 3 percent of people had.
Those working in nursing homes and healthcare workers were more likely to have antibodies, compared to those who were not, with 16 percent of nursing home workers and 15 healthcare workers showing antibodies, versus 5 percent in the rest of the population.
People from Black, Asian, and other ethnic communities also had higher rates – 17 percent, 12 percent, and 12 percent respectively – compared to white British, who had a rate of 5 percent. Age also played a role. Those aged 18 to 34 were most likely to have antibodies – 8 percent of those tested – compared to those over 65, for whom the rate was just 3 percent. Poorer people also had higher levels of antibodies, 7 percent, versus those in wealthier areas, who had an antibody rate of 5 percent. In addition, a third of those with antibodies reported no symptoms at all, and this was even higher in people aged over 65, of whom nearly half reported no symptoms.
According to the authors, as the epidemic increased in March and April it "became more concentrated in specific groups" including Black, Asian and other minority ethnic groups, nursing home and healthcare workers, and those living in larger households and deprived areas. "While these associations were partially attenuated in the adjusted analyses," they wrote in the paper, "they remained important predictors, and reflect starkly uneven experience of the COVID-19 epidemic across society."
According to the UK government, a follow-on study will be carried out this fall and another 200,00 people will be tested for antibodies.
Such antibody tests are only being used for surveillance measures in the UK currently, as no antibody fingerpick test has met the criteria of the UK Medicines and Healthcare Products Regulatory Agency for individual use.
Connected to the REACT-2 study, researchers published a separate paper this week in the journal Thorax concerning the evaluation of different lateral flow assays for detecting antibodies to SARS-CoV-2, in which they reported varying sensitivities and specificities for the tests assessed.
"These results emphasise the need to evaluate new tests in the population of intended use and demonstrate that laboratory performance cannot be assumed to be a surrogate for finger-prick testing," the authors wrote. Based on its sensitivity, specificity, and ability to be used at scale, they selected the Fortress assay for the REACT-2 seroprevalence study.
According to the World Health Organization, there have been roughly 313,000 confirmed cases of COVID-19 in the UK since the pandemic began late last year, including nearly 47,000 deaths to date.